The HN55 is a proportional liquid chemical injector; it injects a precise amount of chemical in proportion to a volume of water. The HN55 does not use electricity. It runs off of water flows as low as one gallon per hour and will work with gravity via a water drop of as little as 5 feet (1.5 meters)! The HN55 utilizes a unique diaphragm driven water motor and a hardened positive displacement chemical pump ensuring a high level of accuracy!